Catalysts for ring-opening copolymerization of cycloolefins

ABSTRACT

A catalyst for the ring-opening copolymerization of a hexachlorocyclopentadiene-1,5-cyclooctadiene adduct and a cycloolefin, other than cyclohexene, having 4 to 12 carbon atoms and containing at least one non-conjugated vinylene double bond. Owing to modification by oxy bidentate-type ligands, the chlorotungsten catalyst system affords a more favorable comonomer reactivity ratio and is thus utilized. The catalyst comprises a compound of (a) the reaction product of tungsten hexachloride and a 1,2- or 1,3- dioxy compound; and a compound (b) having the formula R-AlCl 2  where R is an alkyl group having from 2 to 5 carbon atoms.

TECHNICAL FIELD

The present invention relates to composition of matter and use of acatalyst system for the ring-opening copolymerizations of ahexachloro-cyclopentadiene-1,5-cyclooctadiene Diels-Alder adduct, see(I), hereinafter referred to as Hex COD, and a cycloolefin other thancyclohexene which contains 4 to 12 carbon atoms and possesses at leastone non-conjugated vinylene --CH═CH-- double bond. ##STR1## The oxybidentate-type ligand modified catalyst system described herein moreeffectively incorporates the Hex COD monomer into the polymer systemduring the early stages of the polymerization, relative to the samecopolymerization initiated by the prior artchlorotungsten/organoaluminum cocatalyst system. That is, a morefavorable comonomer reactivity ratio is achieved by the catalyst of thisinvention.

BACKGROUND ART

Ring-opening polymerization refers to a process whereby cycloolefins, inthe presence of an olefin metathesis catalyst, form high molecularweight polyalkenamers. ##STR2## It should be noted that inpolyalkenamers resulting from the ring-opening polymerization ofcycloolefins, the repeating polymer segments contain essentially thesame number of carbon atoms and double bonds as the cyloolefinpolymerized. This is to be contrasted with addition polymers preparedfrom acyclic olefins and diolefins, wherein the polymer segments containone less double bond than the employed olefin or diolefin monomercontained.

The present invention is specific for ring-opening copolymerizations ofHex COD (I) and a cycloolefin comonomer as defined above. Representativeof such cycloolefins are cyclopentene, cyclooctene and1,5-cyclooctadiene. Owing to the possession of chlorine atoms,copolymers prepared with Hex COD (I) possess oil-, chemical-, andflame-resistant properties which are useful in numerous applications andare described in an earlier patent, U.S. Pat. No. 3,634,374, grantedJan. 11, 1972.

Copolymerization of Hex COD (I) can be initiated by conventionaltungsten-based olefin metathesis catalyst system, as set forth in U.S.Pat. No. 3,597,403 granted Aug. 3, 1971; U.S. Pat. No. 3,634,374 grantedJan. 11, 1972; U.S. Pat. No. 3,722,255 granted Nov. 13, 1973; U.S. Pat.No. 3,867,361 granted Feb. 18, 1975; U.S. Pat. No. 3,932,373 grantedJan. 13, 1976; and U.S. Pat. No. 3,943,116 granted Mar. 9, 1976.However, with the use of such prior art catalysts, the copolymerizationsare marked by the phenomenon that by comparison with the chargedcomonomer ratio, only a very small level of the chlorine-containing HexCOD comonomer is incorporated into the copolymer during the initial andearly stages of the polymerization, owing to its relatively lowerreactivity. Hence, it is only when the concentration of the cycloolefincomonomer is substantially diminished during the polymerization that thechlorine content of the copolymer gradually approaches the theoreticallevel based on the initial comonomer charge. One of the primarydisadvantages of this feature is that the chlorine-content desired for aparticular copolymer is not achieved when less than quantitative (100percent) yields of the copolymer are obtained.

DISCLOSURE OF INVENTION

It is therefore an object of the present invention that the catalystsystem described in this specification render the chlorine-containingHex COD monomer more competitive in the copolymerizations. That is, itsuse affords a relatively more favorable Hex COD/cycloolefin comonomerreactivity ratio in that during the early stages of the polymerization,as well as during the latter stages, the chlorine content of thecopolymer more closely approaches that expected from the comonomercharge employed.

In general, a method for copolymerizinghexachlorocyclopentadiene-1,5-cyclooctadiene and a cycloolefin, otherthan cyclohexene, having from 4 to 12 carbon atoms, comprises the stepsof: utilizing a catalyst consisting of (a) the reaction product of fromabout 0.9 to about 1.5 moles of tungsten hexachloride and one mole of a1,2- or 1,3-dioxy compound selected from the group consisting of2,4-pentadione, 2-formylphenol, 1,2-dihydroxybenzene,1,3-diphenyl-1,3-propanedione, and (b) a compound having the formulaR-AlCl₂ wherein R is an alkyl group having from 2 to 5 carbon atoms, themolar ratio of (b) to (a) ranging from about 2 to about 6, and carryingout said copolymerization at a temperature of from about minus 10 toabout 40° C.

In general, a catalyst for the ring-opening copolymerization of Hex CODand a cycloolefin having from 4 to 12 carbon atoms other thancyclohexene, said cycloolefin containing at least one non-conjugateddouble bond, comprising: a compound of (a) the reaction product oftungsten hexachloride and a 1,2- or 1,3-dioxy compound selected from thegroup consisting of 2,4-pentadione, 2-formylphenol,1,2-dihydroxybenzene, 1,3-diphenyl-1,3-propanedione, and combinationsthereof; and (b) a compound having the formula R-AlCl₂ wherein R is analkyl group having from 2 to 5 carbon atoms, the molar ratio of (b) to(a) ranging from about 2 to about 6, the amount of said tungstenchloride to said dioxy compound ranging from about 0.9 moles to about1.5 moles.

BEST MODE FOR CARRYING OUT THE INVENTION

The present catalyst system comprises (A) the reaction product oftungsten hexachloride (WCl₆) and an approximately equimolar amount of a1,2- or 1,3-dioxy compound selected from the group consisting of2,4-pentadione, 2-formylphenol, 1,2-dihydroxybenzene (catechol), and1,3-diphenyl-1,3-propanedione; and (B) an organoaluminum compound of theformula

    R-AlCl.sub.2

wherein R represents an alkyl group having from 2 through 5 carbonatoms. Representative of such monoalkylaluminum dichlorides areethylaluminum dichloride, n-propylaluminum dichloride, isobutylaluminumdichloride, and the like.

That the more favorable Hex COD/cycloolefin comonomer reactivity ratioobtained with WCl₆ moldified with a dioxy compound, i.e., compound (A),is not due simply to the number of oxygen atoms attached to the centraltungsten atom, can be readily ascertained from Table I where the presentcatalyst system is compared with the typical prior art tungsten catalystlikewise possessing two oxygen atoms, but from two separate ligands.

No definite explanation is known for the improved comonomer reactivityafforded by the present catalyst system, but it is interesting to notethat a basic structural feature of the 1,2- and 1,3-dioxy compoundswhich can serve as modifiers of WCl₆ to give the (A) component, is thateach of these can conceivably act as a bidendate leading to one of anumber of structures in which the two oxygen atoms of the bidentateligand can either both be bonded to the tungsten atom, or one bonded andthe other coordinated with the tungsten atom as illustrated: ##STR3##Hence, the chelation of the central tungsten atom may be a criticalfactor in the unique effect that this catalyst has on the comonomerreactivity in Hex COD copolymerizations.

The (A) component of the catalyst system is prepared by mixing fromabout 0.9 to about 1.5 moles, or preferably an equimolar amount of WCl₆to one of the above-defined dioxy modifiers at ambient temperatures inan inert solvent such as benzene, chlorobenzene, or cyclohexane, andbubbling an inert gas such as nitrogen, etc., through the resultingsolution to remove all traces of the hydrogen chloride gaseousby-product.

The catalysts employed in this invention are prepared by mixing thecomponents by known techniques. Thus, the catalysts may be prepared by"preformed" or in situ techniques. In the "preformed" method, thecatalyst components are mixed together prior to exposure of any of thecatalyst components to the cyclic monomers to be used in thepolymerization reaction. In the in situ method, the catalyst componentsare added separately to the cyclic monomers in the polymerizationmixture. In the practice of this invention, the latter method ispreferred, and in the preferred order wherein the tungsten component (A)is added first and, then, the aluminum component (B).

It has been found that good results are obtained in the practice of thisinvention when the molar relationship of the aluminum component (B) tothe tungsten component (A) of the catalyst system is from 2/1 to 6/1.More preferred are (B)/(A) molar ratios of between 3.5/1 to 4.5/1. Theamount of tungsten catalyst employed is 1 gram of the tungstenhexachloride before modification to from about 1,800 grams to about2,500 grams of the comonomers.

With respect to the cycloolefin comonomers, compounds which can beutilized include cyclopentene, cyclooctene, 1,5,9-cyclododecatriene, and1,5-cyclooctadiene. The preferred cycloolefins are cyclopentene and1,5-cyclooctadiene.

The temperature range in which the polymerization can be carried out isfrom about minus 10° C. to about 40° C., with from about 0° C. to about10° C. being preferred. Although atmospheric pressure is generallyutilized, the reaction may be carried out in a slight vacuum or underslight pressure.

The copolymers of the present invention are particularly suited for useas in hoses, brake linings, motor mounts, and other rubber items whereingood solvent and flame resistance is desired.

The following examples are set forth to further illustrate the practiceof this invention.

EXAMPLE I

A 55 percent solution by weight of Hex COD and cyclopentene incyclohexane was passed through a column packed with silica gel andalumina. Previously dried four ounce bottles were each charged with 80ml of solution, (that is, 44 grams of comonomers), and sparged withnitrogen for 15 seconds before closing with a self-sealing cap. Thebottles were cooled to 0° C. Using a syringe, 0.5 ml of a 0.05 Mcatalyst solution (A) set forth in Table I, and 0.45 ml of 0.2 M EADC(ethylaluminum dichloride) solution were injected respectively into thebottle through the self-sealing caps. The reaction temperatures weremaintained at 0° C. to 5° C.

After 1 to 6 hours, the polymerizations were terminated by injecting 1ml of isopropylalcohol into the bottle and shaking the viscous contents.The polymer products were isolated through coagulation, by pouring thereaction mixture into isopropylalcohol solvent. The polymers were driedunder vacuum at 55°-65° C., and obtained in 97 to 100 percent yields.

                                      TABLE I                                     __________________________________________________________________________                              % Cl FOUND                  % Cl after              OXY-BIDENDATE   % CONVERSION                                                                            OXY-BIDENTATE               COMPLETE                CATALYSTS       TO POLYMER                                                                              CATALYST   PHENOXY WCl.sub.5                                                                       (EtO).sub.2 WCl.sub.4                                                                CONVERSION              __________________________________________________________________________      (2,4-pentanedione)WCl.sub.5                                                                 3         10         (2)       (--)   36                                      20        29         (9)       (7)    36                        (2-formylphenoxy)WCl.sub.5                                                                  16        18         (7)       (4.8)  36                                      42        24          (18)      (15)  36                        (1,2-dihydroxybenzene)WCl.sub.4                                                             6         29         (3)       (--)   36                                      20        30.5       (9)       (7)    36                      __________________________________________________________________________

From the chlorine contents obtained from the copolymers at variousconversions (Table I), it can be readily seen that a significantlyhigher ratio of the Hex COD chlorine-containing monomer to comonomer isobtained during the earlier stages of the copolymerizations when thepresent catalyst system is employed, compared with those obtained usingthe prior art catalysts.

While in accordance with the patent statutes, the preferred embodimentand the best mode of the invention have been set forth in detail, thescope of the invention is to be measured by the attached claims.

What is claimed is:
 1. A catalyst for a ring-opening copolymerization,consisting of:a compound of (a) the reaction product of tungstenhexachloride and a 1,2- or 1,3-dioxy compound selected from the groupconsisting of 2,4-pentadione, 2-formylphenol,1,3-diphenyl-1,3-propanedione, said reaction product forming a bidentateligand; and a compound (b) having the formula R-AlCl₂ wherein R is analkyl group having from 2 to 5 carbon atoms, the molar ratio of (b) to(a) ranging from about 2 to about 6, the amount of said tungstenchloride to said dioxy compound ranging from 0.9 moles to about 1.5moles, said bidentate ligand causing a more favorable comonomerreactivity ratio in the ring-opening copolymerization of Hex COD monomerand a cycloolefin monomer other than cyclohexene, said cycloolefinhaving from 4 to 12 carbon atoms and at least one non-conjugated doublebond.
 2. A catalyst according to claim 1, wherein said organoaluminumcompound is selected from the group consisting of ethylaluminumdichloride, isobutylaluminum dichloride, n-propylaluminum dichloride. 3.A catalyst according to claim 2, wherein said molar ratio of (b) to (a)ranges from about 3.5 to about 4.5.
 4. A catalyst according to claim 3,wherein said dioxy compound is 2,4-pentadione, and wherein saidorganoaluminum compound is ethylaluminum dichloride.